Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-ioam-sr-04
Loa Andersson <loa@pi.nu> Thu, 07 January 2021 05:12 UTC
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To: Mach Chen <mach.chen@huawei.com>, Greg Mirsky <gregimirsky@gmail.com>
Cc: Stewart Bryant <stewart.bryant@gmail.com>, "Rakesh Gandhi (rgandhi)" <rgandhi=40cisco.com@dmarc.ietf.org>, mpls <mpls@ietf.org>, "draft-gandhi-mpls-ioam-sr@ietf.org" <draft-gandhi-mpls-ioam-sr@ietf.org>, mpls-chairs <mpls-chairs@ietf.org>
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From: Loa Andersson <loa@pi.nu>
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Date: Thu, 07 Jan 2021 13:12:35 +0800
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Subject: Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-ioam-sr-04
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Maach, If it is a requirement from iOAM to do hop by hop processing, then the SPL/eSPL is a very blunt tool, there is is always a risk that the (e)SPL label that indicate the special behavior is below the maximum stack depth that can be scanned. Right? If we create a FEC that says "this packet has a hop by hop processing requirement, go find the ACH-header immediately after the label stack to see what you need to do." That would not solve the immediate problem but also be useful for the future. /Loa On 07/01/2021 11:50, Mach Chen wrote: > Hi all, > > IMHO, I think the key issue is that there is no hop-by-hop option in > MPLS, but the iOAM requires that. > > There are three potential options: > > 1)Scan the stack and find the (e)SPL label that indicate the special > behavior; > > 2)Introduce an (e)SPL and always keep it on the top of the label stack; > > 3)Use the way as Stewart suggested, a new FEC, just like the SFL; > > Best regards, > > Mach > > *From:*Greg Mirsky [mailto:gregimirsky@gmail.com] > *Sent:* Thursday, January 7, 2021 11:30 AM > *To:* Loa Andersson <loa@pi.nu> > *Cc:* Stewart Bryant <stewart.bryant@gmail.com>; Rakesh Gandhi (rgandhi) > <rgandhi=40cisco.com@dmarc.ietf.org>; mpls <mpls@ietf.org>; > draft-gandhi-mpls-ioam-sr@ietf.org; mpls-chairs <mpls-chairs@ietf.org> > *Subject:* Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-ioam-sr-04 > > Hi Loa, et al., > > RFC 8169 uses TTL expiration to achieve processing at each RTM-capable > node. That approach creates a state in transient nodes and may not fit > with the "no state" paradigm of the Segment Routing. > > And I've got a question. AFAIK, the presence of ACH in an MPLS LSP is > indicated by GAL. Is there an intention to introduce another (E)SPL for > that? > > Regards, > > Greg > > On Wed, Jan 6, 2021 at 7:20 PM Loa Andersson <loa@pi.nu > <mailto:loa@pi.nu>> wrote: > > Stewart, > > If we want to make sure that packets are processed at evey node, is the > new FEC complementary to the ACH-header or an alternative? > > /Loa > > On 05/01/2021 00:30, Stewart Bryant wrote: > > > > > >> On 4 Jan 2021, at 14:38, Rakesh Gandhi (rgandhi) > >> <rgandhi=40cisco.com@dmarc.ietf.org <mailto:40cisco.com@dmarc.ietf.org> > >> <mailto:rgandhi <mailto:rgandhi>=40cisco.com@dmarc.ietf.org > <mailto:40cisco.com@dmarc.ietf.org>>> wrote: > >> > >> <RG> Yes, this is similar to the entropy label where a mid-point node > >> needs to scan the label stack to find the indicator label. We can add > >> some text to clarify this. There is already an optimization to use a > >> different indicator label for HbH compared to E2E case to > >> unnecessarily avoid parsing the IOAM data fields. > > > > The EL is entirely optional to process. It is no more than a hint to use > > in ECMP and there is no architectural requirement to find it to operate > > correctly. > > > > If iOAM is purely a option then you could scan the stack and hope that > > you can reach down far enough to find it. Though there is a fight to see > > who gets to be the lowest label in range of the forwarding parser. > > > > If you want to be sure that iOAM is processed HxH then you really need > > to run it on a new FEC with that behaviour built into the FEC. That > > would be the architected way of doing this in MPLS. > > > > - Stewart > > > > > > > > _______________________________________________ > > mpls mailing list > > mpls@ietf.org <mailto:mpls@ietf.org> > > https://www.ietf.org/mailman/listinfo/mpls > <https://www.ietf.org/mailman/listinfo/mpls> > > > > -- > > Loa Andersson email: loa@pi.nu <mailto:loa@pi.nu> > Senior MPLS Expert loa.pi.nu@gmail.com <mailto:loa.pi.nu@gmail.com> > Bronze Dragon Consulting phone: +46 739 81 21 64 > > _______________________________________________ > mpls mailing list > mpls@ietf.org <mailto:mpls@ietf.org> > https://www.ietf.org/mailman/listinfo/mpls > <https://www.ietf.org/mailman/listinfo/mpls> > -- Loa Andersson email: loa@pi.nu Senior MPLS Expert loa.pi.nu@gmail.com Bronze Dragon Consulting phone: +46 739 81 21 64
- [mpls] MPLS-RT Review of draft-gandhi-mpls-ioam-s… Andrew G. Malis
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Loa Andersson
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… tom petch
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Greg Mirsky
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Andrew G. Malis
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Rakesh Gandhi
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Andrew G. Malis
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Loa Andersson
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Loa Andersson
- [mpls] MPLS-RT Review of draft-gandhi-mpls-ioam-s… Mach Chen
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Tianran Zhou
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Loa Andersson
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Andrew G. Malis
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Rakesh Gandhi (rgandhi)
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Stewart Bryant
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Tianran Zhou
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Loa Andersson
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Greg Mirsky
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Loa Andersson
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Mach Chen
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Loa Andersson
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Mach Chen
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Greg Mirsky
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Mach Chen
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Eric Gray
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Eric Gray
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Rakesh Gandhi (rgandhi)
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Loa Andersson
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Mach Chen
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Stewart Bryant
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Stewart Bryant
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Mach Chen
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Mach Chen
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Stewart Bryant
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… John E Drake
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Jeff Tantsura
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Rakesh Gandhi (rgandhi)
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Loa Andersson
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Loa Andersson
- Re: [mpls] MPLS-RT Review of draft-gandhi-mpls-io… Rakesh Gandhi